Background: Doppler ultrasound (duplex) tests are commonly applied after carotid endarterectomy to detect possible recurrent stenosis. The appropriate frequency and the benefits are unknown. We investigated the costs and effects of various follow-up strategies to determine the optimal strategy after carotid endarterectomy.
Methods: Using decision-analytic methods, a Monte Carlo Markov model was constructed. Probabilities and costs were obtained by systematic literature review. From empirical data regarding restenosis, a disease model was constructed to test the effect of various follow-up strategies using duplex testing and angiography. Main outcome measures were quality-adjusted life-years (QALYs), probability of stroke, and costs (for both the Dutch and the American situation).
Results: The average quality-adjusted life expectancy for a 66-year-old patient was 6.31 years for the symptom-guided strategy (with duplex scanning only being performed in case of symptoms of cerebral ischemia). The mean lifetime costs for this strategy were $5 600 for the US and 4 600 Euro for the Netherlands. The cumulative probability of stroke was 13%. Yearly routine duplex tests up to 5 years after operation resulted in similar QALYs and a similar probability of stroke, but higher costs ($7 300 for the US and 5 600 Euro for The Netherlands situation). No other strategy, including routine duplex surveillance, increased QALYs. When MR instead of conventional angiography was used as confirmatory test, no improvement was observed either.
Conclusions: Routine duplex surveillance does not result in an increase in quality-adjusted life expectancy, but it does increase costs. After successful carotid endarterectomy, a symptom-guided follow-up is an appropriate approach.